(1) Field of the Invention
The present invention relates to a concrete joint sealant plate and process for manufacturing thereof.
(2) Prior Art
In the wide areas of the concrete pavements such as roads, airports (aprons, taxi ways), parking lots, cargo collecting areas, etc., and in the concrete constructions are used various kinds of joint sealant plates such as contraction joint sealants for introducing into a predetermined area cracks due to the contraction of the concrete plates and expansion joint sealants for preventing the blow-up due to the expansion of the concrete plates as the temperature rises, and the construction joint sealants provided from the necessity in constructing. In order to prevent rain water or the like from invading into the base ground and foreign matters from invading into the joints, and to assure the flatness of the concrete plates via the concrete joints, poured joint sealants and joint sealant plates have been heretofore used in the joints.
The conventional joint sealant plates employed for this purpose include (A) the bituminous concrete joint sealant plate which is produced by kneading the bituminous substance, mainly petroleum asphalt, and a filler together, with heating, forming the mixture into a plate, and covering the plate thus produced with asphalt papers on both sides thereof, (B) the bituminous fibre joint sealant plate which is produced by impregnating a fibrous plate with hot-melted petroleum asphalt or petroleum asphalt dissolved into petroleum-base solvent (the latter being called "cutback asphalt"), (C) the foamed joint sealant plate which is obtained by foaming resin or rubber.
However, known bituminous joint sealant plates have the drawbacks that the degree at which the sealant extrudes onto or over the surfaces of the paved concrete plates due to the expansion and contraction of the concrete plate is large and the physical properties of the plates change to a large extent and experience poor recovery following the warm-cold weather cycle. The foamed concrete sealant plate has the drawbacks that it is poor in workability and inconvenient in handling due to its low rigidity; and it is likely to deflect in applying. The bituminous fibre joint sealant plate in which the fibrous plate is impregnated with the hot-melted asphalt has the drawbacks that there are dangers or disadvantages due to the content of the asphalt becoming greater than 65%; the concrete joint sealant plates adhere to one another during storage in summer; its physical properties change to a large extent with the outdoors temperature; and it largely extrudes over or onto the surfaces of the concrete pavement. Further, the bituminous fibre joint sealant plate which is impregnated with the cutback asphalt has the danger that it is likely to catch fire owing to its high content of the organic solvent during the operation of impregnation and drying. This cutback type asphalt fibre joint sealant plate is difficult to produce so as to meet ASTM-D 1751 which is the standard norm specifying the fibre joint sealant plate for building and concrete pavements. ASTM-D 1751 specifies the values as to extrusion, recovery etc. (See Table 2 below)